1. Field of the Invention
This invention generally relates to an improved lock rod clamping apparatus for detachably connecting a tool unit to a tool supporter, and is particularly concerned with a side activated clamping apparatus using mechanical advantage.
2. Description of the Prior Art
Clamping mechanisms for detachably connecting a tool unit to a tool supporter are well known in the art. Such mechanisms are typically used in machining operations where the tool unit holds a cutting insert that is moved into and out of cutting engagement with a rotating metal workpiece. The clamping apparatus allows different tool units holding different cutting inserts to be quickly attached to and detached from the tool supporter which in turn is connected to a device that controls the movement of the tool unit with respect to the workpiece.
One of the most commercially successful clamping mechanisms includes a cylindrically-shaped canister that is mateable with the tubular shank of a tool unit and which includes apertures for admitting locking elements into locking engagement with recesses present in the tool unit. The locking elements, which are typically spherical, are radially moved through the apertures in the canister by means of a reciprocating lock rod having cam portions that engage the locking elements. Examples of such a clamping mechanism are disclosed in Erickson U.S. Pat. Nos. 4,708,040; 4,747,735; 4,836,068, and 4,932,295, each of which is assigned to Kennametal Inc. located in Latrobe, Pa.
Such a clamping mechanism is illustrated in FIG. 1. Here, a side cross-sectional view of the distal end 53 of a canister 39 is shown which includes an aperture 54a in the form of a cylindrical bore through the wall of the member 39. The inner diameter of the circular bore forming the aperture 54a closely approximates the outer diameter of the spherical locking element 57a. The lock rod 60 includes a cam portion 64a having a spherical depression 66 which tapers off into a ramp 68. When the spherical locking element 57a is seated in the depression 66, and the stop flange 70 of the lock rod 60 abuts annular wall 71, the spherical element 57a is in a non-locking position which would allow the tubular shank 16 of a tool unit 10 to be inserted into the annular recess 59 of the coupling member 43. However, when the lock rod 60 is moved to the right in the position illustrated, the ramp 68 of the cam portion 64a wedgingly engages and raises the spherical locking element 57a into the locking position. In such a position, the spherical locking element 57a will wedgingly and lockingly bear against an angled aperture wall 30 of the tool unit 10.
The prior art tool unit 10 as illustrated in FIGS. 2 and 3 includes a forward end 12 for holding a cutting tool, and a rearward tubular shank 16 for connection to a tool supporter. The forward end 12 includes a recess or pocket 14 which is conventional in design for receiving an indexable cutting insert, locking bracket, and shim (not shown). At the junction between the forward end 12 and the tubular shank 16 is an annular abutment face 17 for engagement with the annular face of a tool supporter when the tool unit is connected to such a supporter by way of a clamping mechanism. The abutment face 17 is planar and is orthogonally oriented with respect to the longitudinal axis L of the tubular shank 16.
As is indicated in FIG. 3, the tubular shank 16 has a frusto-conical shape and includes a pair of opposing openings 18a,b for receiving spherical locking elements of the clamping mechanism which is described hereinafter. The walls 20 of the openings 18a,b are, in part, cylindrical around their circumference and angled (as shown in FIG. 3) for facilitating the locking engagement between the shank 16 and the spherical locking elements of the clamping mechanism. The inner surface 22 of the tubular shank 16 is substantially cylindrical in shape to closely mate with the outer surface of the canister of the locking mechanism. The shank outer surface 24 is frusto-conical for the purposes of both centering and stiffening the coupling between the tool unit 10 and a tool supporter. Disposed orthogonally with respect to the opposing openings 18a,b are alignment slots 26 and 28. As will be explained, these slots 26,28 fit into protruding keys (not shown) present in the canister of the clamping mechanism to ensure alignment between the openings 18a,b with the spherical locking elements of the clamping mechanism.
With reference now to FIG. 4, a prior art clamping mechanism 35 is disposed within a prior art tool supporter 37 as shown. The clamping mechanism 35 includes a cylindrically shaped canister 39 mounted within a housing 41 formed from a coupling member 43. The coupling member 43 terminates, at its distal end, in an annular abutment face 44 that confronts the previously discussed abutment face 17 of the tool unit 10 when the coupling member 43 and tool unit 10 are connected. The tool support housing 37 further has a housing member 45 disposed behind the coupling member 43. The canister 39 is affixed to the housing 41 by way of an annular flange 47 secured to the coupling member 43 by bolts 49. Coupling member 43 is in turn secured to the housing member 45 by means of bolts 51. Thus the canister 39 remains stationary relative to the lock rod 60 during the operation of the clamping mechanism 35.
The distal end 53 of the canister 39 includes a pair of opposing apertures 55a,b for admitting locking elements 57a,b in the form of spheres. The locking elements 57a,b are illustrated in solid lines to show their position when the clamping mechanism is unlocked and in phantom lines to show their position when the coupling is in the locked position. It is important to note that the walls of the apertures 55a,b are cylindrical bores having an inner diameter that is slightly larger than the outer diameter of the locking spheres 57a,b. The distal end 53 of the canister 39 also includes the previously mentioned pair of alignment lugs (not shown) disposed at right angles to the apertures 55a,b. A frusto-conically shaped annular recess 59 is defined between the outer surface of the distal end 62 of the canister 39, and the inner surface of the coupling member 43 for receiving the tool unit 10.
In addition to the canister 39 and locking spheres 57a,b, the clamping mechanism 35 of the invention further includes lock rod 60 which is reciprocally movable along an axis A into the position illustrated in phantom. The lock rod 60 has a distal end 62 concentrically disposed within and slidably movable with respect to the distal end 53 of the canister 39. The distal end 62 of the lock rod 60 includes opposing cam portions 64a,b for radially moving the locking spheres 57a,b into and out of the annular recess 59. To this end, each of the cam portions 64a,b includes a depression 66 which is partially complementary in shape to the spheres 57a,b, and a ramp 68 extending from one side of the depression 66 toward the distal end 62 of the lock rod 60. The cam portion 64 defines the path of the locking elements along the lock rod. This path is also known as the ball track.
Lock rod 60 further has an integrally formed stop flange 70 that engages an annular wall 71 of the canister 39 to arrest the stroke of the lock rod 60 in the distal direction. The proximal end 63 of the lock rod 60 is formed from a cylindrical shaft 72 slidably mounted within the proximal end of the canister 39. Shaft 72 terminates in a spring retainer 73. A spring pack formed from stacked Belleville washers 74 constantly applies a tensile force to the spring retainer 73 that biases the lock rod 60 in the locking position illustrated in phantom.
The distal end 62 of the lock rod 60 is used to physically bump the tool unit 10 from the coupling member 43 when the tool unit 10 is to be released. For that reason, if the tool unit 10 must be pushed out of the coupling member 43 for release, then the distal end of the lock rod 60 must be positioned relative to the tool unit 10 for such contact.
The clamping mechanism 35 operates by applying a force and moving the lock rod 60 to the left against the force of the spring pack washers 74. The tubular shank 16 (FIG. 3) of the tool unit 10 is inserted into the annular recess 59 and by removing the applied force on the lock rod 60, the spring pack washers 74 will force the lock rod 60 to the right, causing the locking elements 57a,b to move radially outwardly along the ramps 68 (FIG. 1) and to engage the angled wall 30 of the opening 18a of the tool unit shank 16.
In this prior art design, aperture 54a of the canister 39 is a cylindrical bore extending perpendicular to the longitudinal axis L of the clamping mechanism 35.
It has been discovered that by angling the canister aperture wall located opposite the angled wall 30 of the tool unit shank 16, the clamping force on the tool unit 10 may be increased over that of a non-angled wall using the same force on a lock rod 60 having the same ramp angle. Directing attention to FIG. 5, this is accomplished by tilting the aperture wall 76, which is opposite aperture wall 75. The aperture wall 76 of each of the canister apertures 55a,b is tilted similarly to the aperture wall 75. More specifically, wall 76 is tilted at an angle between about 10.degree. and 20.degree., preferably 15.degree., with respect to axis R which extends radially from the longitudinal axis L. Such a tilting of the aperture wall 76 has the advantage of increasing the gripping force of the clamping mechanism 35.
A clamping mechanism utilizing this arrangement is disclosed in U.S. Pat. No. 5,694,820 which is assigned to Kennametal Inc. and hereby incorporated by reference.
The increased clamping force is best understood with reference to angles M and N shown in FIG. 5. Where the locking sphere 57a is pushed radially outwardly into the locked position illustrated in FIG. 5, its spherical walls engage both the angle portion 30 of the aperture walls of the tool unit 10 and the tilted wall 76 of the aperture 55a at an angle M. Angle M is defined by the projection of lines from aperture wall 76 and the angled portion of the tool unit aperture walls 30. This projection intersects at origin 77.
On the other hand, angle N is defined by line R, which reflects the previous orientation of aperture wall 76 and the angled portion of the tool unit aperture walls 30. The locking sphere 57a wedgingly engages these surfaces, by forced displacement from the ramp 68 of the lock rod 60. Since angle M is smaller than angle N, the locking sphere 57a generates a greater mechanical advantage between those surfaces defined by angle M than those defined by angle N. This modified arrangement provides a clamping force on the order of 30% higher than that clamping force generated with the original arrangement.
While such a prior art clamping mechanism provides increased clamping forces for an arrangement in which the lock rod moves longitudinally in the clamping mechanism housing, in many clamping mechanisms the lock rod is operated from the side of the clamping mechanism. U.S. Pat. No. 4,736,659 is directed to such a side activated mechanism and is co-assigned to Kennametal Inc. and Krupp Widia GmbH and hereby incorporated by reference. Such side activated clamping mechanisms, as they currently exist, are not operational using a canister having apertures with angled walls. The angled walls of the canister cause the locking balls to move along the longitudinal axis of the clamping mechanism and this movement would force the balls off the ball track of a side activated lock rod.
It would be advantageous if a design were available by which the mechanical advantage heretofore discussed would be available to side activated clamping mechanisms.